Links

Research & Scholarship

Current Research and Scholarly Interests

Dr. Tremmel studies sex differences in cardiovascular disease. She is currently investigating sex differences in coronary endothelial function, plaque deposition, and the microcirculation of women and men who present with chest pain, but have normal appearing coronary arteries by angiography. She is also leading Stanfords participation in the multi-center VIRGO trial, which is evaluating sex differences in young patients who present with myocardial infarction. Other active research projects include sex differences in chronic total coronary occlusions, the impact of stress on anginal symptoms, and vascular access site complications. Dr. Tremmel keeps Stanfords Tako-tsubo Patient Registry and is conducting a multi-center study to investigate the relationship of stress and coping to genetic polymorphisms in patients with Tako-tsubo.

The TAXUS Libertē Post-Approval Study is an FDA-mandated prospective, multi-center study
designed to collect real-world safety and clinical outcomes in approximately 4,200 patients
receiving one or more TAXUS Liberté Paclitaxel-Eluting Stents and prasugrel as part of a
dual antiplatelet therapy (DAPT) drug regimen.
This study will also contribute patient data to an FDA-requested and industry-sponsored
research study that will evaluate the optimal duration of dual antiplatelet therapy (DAPT
Study).

Stanford is currently not accepting patients for this trial.For more information, please contact Yvonne Strawa, (650) 498 - 7028.

This is a research study evaluating possible causes of chest pain (or an anginal equivalent,
such as fatigue resulting in a decrease in exercise tolerance, shortness of breath, or back,
shoulder, neck, or jaw pain) in people with no evidence of significant coronary artery
disease on their coronary angiogram (pictures of the blood vessels in the heart). The
purpose of the research study is to determine if there is diffuse atherosclerosis (plaque)
not appreciated by angiography, or if the coronary endothelium (lining of the blood vessels
in the heart) and/or microcirculation (small vessels in the heart that are not easily seen
with an angiogram) are not functioning properly in those who have chest pain (or an anginal
equivalent), but normal coronary arteries on angiography. Specifically, we are interested if
these findings are more common in women than men.

Abstract

Giant coronary aneurysms are rare. We present a 25-year-old woman with a known history of non-Kawasaki/nonatherosclerotic bilateral coronary aneurysms. She was transferred to our facility with acute coronary syndrome complicated by cardiogenic shock. Angiography demonstrated giant bilateral coronary aneurysms and complete occlusion of the left anterior descending (LAD) artery. Emergent coronary artery bypass grafting was performed. Coronary artery bypass grafting is the preferred approach for addressing giant coronary aneurysms. Intervention on the aneurysm varies in the literature. Aggressive revascularization is recommended in the non-Kawasaki/nonatherosclerotic aneurysm patient, and ligation should be performed in patients with thromboembolic phenomena.

Abstract

Although a myocardial bridge (MB) is often regarded as a benign coronary variant, recent studies have associated MB with focal myocardial ischemia. The physiological consequences of MB on ventricular function during stress have not been well established.We enrolled 58 patients with MB of the left anterior descending artery, diagnosed by intravascular ultrasound. Patients underwent invasive physiological evaluation of the MB by diastolic fractional flow reserve during dobutamine challenge and exercise echocardiography. Septal and lateral longitudinal strain (LS) were assessed at rest and immediately after exercise and compared with strain of matched controls. Absolute and relative changes in strain were also calculated. The mean age was 42.5±16.0 years. Fifty-five patients had a diastolic fractional flow reserve ≤0.76. At rest, there was no significant difference between the 2 groups in septal LS (19.0±1.8% for patients with MB versus 19.2±1.5% for control, P=0.53) and lateral LS (20.1±2.0% versus 20.0±1.6%, P=0.83). With stress, compared with controls, patients with MB had a lower peak septal LS (18.9±2.6% versus 21.7±1.6%, P<0.001) and lower absolute (-0.1±2.1% versus 2.5±1.3%, P<0.001) and relative change (-0.6±11.2% versus 13.1±7.8%, P<0.001) in septal LS, whereas there was no significant difference in lateral LS. In multivariate analysis, diastolic fractional flow reserve and length were independent determinants of lower changes in septal LS.Patients with a hemodynamically significant MB, determined by invasive diastolic fractional flow reserve, have significantly lower change in septal LS on exercise echocardiography, suggesting that septal LS may be useful for noninvasively assessing the hemodynamic significance of an MB.

Abstract

Stress-induced cardiomyopathy (SCM) is a reversible cardiomyopathy observed in patients without significant coronary disease. The aim of this study was to assess the incidence and clinical significance of right ventricular (RV) involvement in SCM.We retrospectively analyzed echocardiograms from 40 consecutive patients who presented with SCM at Stanford University Medical Center from September 2000 to November 2010. The primary end point was overall mortality. RV involvement was observed in 20 patients (50%; global RV hypokinesia in 15 patients and focal RV apical akinesia in 5 patients). The independent correlates of RV involvement were older age (odds ratio [OR] 1.09, 95% confidence interval [CI] 1.02-1.7two, P = .01) and LVEF (per 10% decrease: OR 3.60, CI 1.77-7.32; P = .02). At a mean follow-up of 44 ± 32 months, 12 patients (30%) died (in-hospital death in 3 patients). At multivariate analysis, the presence of an RV fractional area change <35% emerged as an independent predictor of death (OR 3.6, CI 1.06-12.41; P = .04).RV involvement is a common finding in SCM, and may present as either global or focal RV apical involvement. Both older age and lower LVEF are associated with a higher risk of RV involvement, which appears to be a major predictor of death.

Abstract

More than 20% of patients presenting to the cardiac catheterization laboratory with angina have no angiographic evidence of coronary artery disease. Despite a "normal" angiogram, these patients often have persistent symptoms, recurrent hospitalizations, a poor functional status, and adverse cardiovascular outcomes, without a clear diagnosis.In 139 patients with angina in the absence of obstructive coronary artery disease (no diameter stenosis >50%), endothelial function was assessed; the index of microcirculatory resistance, coronary flow reserve, and fractional flow reserve were measured; and intravascular ultrasound was performed. There were no complications. The average age was 54.0±11.4 years, and 107 (77%) were women. All patients had at least some evidence of atherosclerosis based on an intravascular ultrasound examination of the left anterior descending artery. Endothelial dysfunction (a decrease in luminal diameter of >20% after intracoronary acetylcholine) was present in 61 patients (44%). Microvascular impairment (an index of microcirculatory resistance ≥25) was present in 29 patients (21%). Seven patients (5%) had a fractional flow reserve ≤0.80. A myocardial bridge was present in 70 patients (58%). Overall, only 32 patients (23%) had no coronary explanation for their angina, with normal endothelial function, normal coronary physiological assessment, and no myocardial bridging.The majority of patients with angina in the absence of obstructive coronary artery disease have occult coronary abnormalities. A comprehensive invasive assessment of these patients at the time of coronary angiography can be performed safely and provides important diagnostic information that may affect treatment and outcomes.

Abstract

With the plethora of clinical trials, it is difficult for busy interventional cardiologists to stay up to date. Therefore, the Society for Cardiovascular Angiography and Interventions (SCAI) publications committee concisely summarized and provided editorial commentary on the most important trials from recent, large international meetings. The intent is to provide this summary every six months to allow quick assimilation of trial results into interventional practice.

Abstract

Patients with a myocardial bridge (MB) and no significant obstructive coronary artery disease (CAD) may experience angina presumably from ischemia, but noninvasive assessment has been limited and the underlying mechanism poorly understood. This study seeks to correlate a novel exercise echocardiography (EE) finding for MBs with invasive structural and hemodynamic measurements.Eighteen patients with angina and an EE pattern of focal end-systolic to early-diastolic buckling in the septum with apical sparing were prospectively enrolled for invasive assessment. This included coronary angiography, left anterior descending artery (LAD) intravascular ultrasound (IVUS), and intracoronary pressure and Doppler measurements at rest and during dobutamine stress. All patients were found to have an LAD MB on IVUS. The ratios of diastolic intracoronary pressure divided by aortic pressure at rest (Pd/Pa) and during dobutamine stress (diastolic fractional flow reserve [dFFR]) and peak Doppler flow velocity recordings at rest and with stress were successfully performed in 14 patients. All had abnormal dFFR (≤0.75) at stress within the bridge, distally or in both positions, and on average showed a more than doubling in peak Doppler flow velocity inside the MB at stress. Seventy-five percent of patients had normalization of dFFR distal to the MB, with partial pressure recovery and a decrease in peak Doppler flow velocity.A distinctive septal wall motion abnormality with apical sparing on EE is associated with a documented MB by IVUS and a decreased dFFR. We posit that the septal wall motion abnormality on EE is due to dynamic ischemia local to the compressed segment of the LAD from the increase in velocity and decrease in perfusion pressure, consistent with the Venturi effect.

Abstract

This study sought to evaluate the impact of sex differences on fractional flow reserve (FFR)-guided percutaneous coronary intervention (PCI).The FAME (Fractional Flow Reserve Versus Angiography for Multivessel Evaluation) study demonstrated that FFR-guided PCI improves outcomes compared with an angiography-guided strategy. The role of FFR-guided PCI in women versus men has not been evaluated.We analyzed 2-year data from the FAME study in the 744 men and 261 women with multivessel coronary disease, who were randomized to angiography- or FFR-guided PCI. Statistical comparisons based on sex were stratified by treatment method.Although women were older and had significantly higher rates of hypertension than men did, there were no differences in the rates of major adverse cardiac events (20.3% vs. 20.2%, p = 0.923) and its individual components at 2 years. FFR values were significantly higher in women than in men (0.75 ± 0.18 vs. 0.71 ± 0.17, p = 0.001). The proportion of functionally significant lesions (FFR ? 0.80) was lower in women than in men for lesions with 50% to 70% stenosis (21.1% vs. 39.5%, p < 0.001) and for lesions with 70% to 90% stenosis (71.9% vs. 82.0%, p = 0.019). An FFR-guided strategy resulted in similar relative risk reductions for death, myocardial infarction, and repeat revascularization in men and in women. There were no interactions between sex and treatment method for any outcome variables.In comparison with men, angiographic lesions of similar severity are less likely to be ischemia-producing in women. An FFR-guided PCI strategy is equally beneficial in women as it is in men.

Abstract

Retroperitoneal hematoma (RPH) increases morbidity and mortality in percutaneous coronary intervention (PCI). High femoral arteriotomy is an independent predictor of RPH, but the optimal angiographic criterion for defining a high puncture is unknown.We retrospectively identified 557 consecutive PCI cases with femoral angiograms. Arteriotomy sites were categorized as high based on three angiographic criteria: at or above the proximal third of the femoral head (criterion A), at or above the most inferior border of the inferior epigastric artery (criterion B), and at or above the origin of the inferior epigastric artery (criterion C). Cases of RPH were then identified.Of the 557 PCI patients, 26 had a high femoral arteriotomy by criterion A, 17 by criterion B, and 6 by criterion C. Among these patients with a high arteriotomy, RPH occurred in four with criterion A, in three with criterion B, and in one with criterion C. Of the three criteria, criterion A most strongly correlated with RPH (odds ratio [OR] 96, 95% confidence interval [CI] 10.3-898.4; p < 0.0001) compared with criterion B (OR 58, 95% CI 8.9 to 372.6; p < 0.0001) or C (OR 27, 95% CI 2.6 to 290.1; p = 0.053). All criteria had high specificity (A, 96%; B, 97%; C, 99%), but the sensitivity was higher with criterion A (80%) than criterion B (60%) or C (20%), and statistically, the use of criterion A led to the most accurate risk-stratification for RPH (A, ? = 0.79; B, ? = 0.59; C, ? = 0.19).Among the three common definitions of high arteriotomy, femoral artery puncture at or above the proximal third of the femoral head is the landmark that most accurately risk stratifies PCI patients for development of RPH.

Abstract

There are conflicting data as to the prevalence of coronary artery disease (CAD) in patients with end-stage liver disease (ESLD) being assessed for liver transplantation (LT). The aims of this study were to compare the prevalence of CAD in patients with alcohol-related versus non-alcohol-related ESLD and to assess the diagnostic utility of dobutamine stress echocardiography (DSE) in predicting angiographically important CAD. Consecutive patients with ESLD being assessed for LT (n = 420, mean age 56 ± 8 years) were identified and divided into groups of those with alcohol-related ESLD (n = 125) and non-alcohol-related ESLD (n = 295). Demographic characteristics, CAD risk factors, results of DSE, and coronary angiographic characteristics were recorded. There were no significant differences in age or CAD risk factors between groups. The incidence of severe CAD (>70% diameter stenosis) was 2% in the alcohol-related ESLD group and 13% in the non-alcohol-related ESLD group (p <0.005). In the 2 groups, the presence of ?1 CAD risk factor was associated with significant CAD (p <0.05 for all). Absence of cardiac risk factors was highly predictive in ruling out angiographically significant disease (negative predictive value 100% for alcohol-related ESLD and 97% for non-alcohol-related ESLD). DSE was performed in 205 patients. In the 2 groups, DSE had poor predictive value for diagnosing significant CAD but was useful in ruling out patients without significant disease (negative predictive value 89% for alcohol-related ESLD and 80% for non-alcohol-related ESLD). In conclusion, there was a significantly lower prevalence of severe CAD in patients with alcohol-related ESLD. These findings suggest that invasive coronary angiography may not be necessary in this subgroup, particularly in the absence of CAD risk factors and negative results on DSE.

Abstract

In response to growing U.S. interest, the Society for Coronary Angiography and Interventions recently formed a Transradial Committee whose purpose is to examine the utility, utilization, and training considerations related to transradial access for percutaneous coronary and peripheral procedures. With international partnership, the committee has composed a comprehensive overview of this subject presented here-with.

Abstract

Although not a definitive treatment, percutaneous coronary intervention offers a palliative benefit to patients with cardiac allograft vasculopathy. Given the superior outcomes with drug-eluting stents (DESs) over bare metal stents (BMSs) in native coronary artery disease, similar improvements might be expected in transplant patients; however, the results have been mixed. Consecutive cardiac transplantation recipients at a single center receiving a stent for de novo cardiac allograft vasculopathy from 1997 to 2009 were retrospectively analyzed according to receipt of a DES versus a BMS. The angiographic and clinical outcomes were subsequently evaluated at 1 year. The baseline clinical and procedural characteristics were similar among those receiving DESs (n = 18) and BMSs (n = 16). Quantitative coronary angiography revealed no difference in the reference diameter, lesion length, or pre-/postprocedural minimal luminal diameter. At the 12-month angiographic follow-up visit, the mean lumen loss was significantly lower in the DES group than in the BMS group (0.19 ± 0.73 mm vs 0.76 ± 0.97 mm, p = 0.02). The DES group also had a lower rate of in-stent restenosis (12.5% vs 33%, p = 0.18), as well as a significantly lower rate of target lesion revascularization (0% vs 19%, p = 0.03). At 1 year, DESs were associated with a lower composite rate of cardiac death and nonfatal myocardial infarction (12% vs 38%, p = 0.04). In conclusion, DESs are safe and effective in the suppression of neointimal hyperplasia after percutaneous coronary intervention for cardiac allograft vasculopathy, resulting in significantly lower rates of late lumen loss and target lesion revascularization, as well as a reduced combined rate of cardiac death and nonfatal myocardial infarction.

Abstract

The adrenergic and histaminergic systems have been reported to have analogous effects on the heart. A case of transient ventricular dysfunction with echocardiographic findings characteristic of stress-induced cardiomyopathy (also known as takotsubo cardiomyopathy) in a patient who had an urticarial transfusion reaction is described. The effect of histamine on ventricular function and its interaction with the adrenergic system are discussed.

Abstract

There is an increasing interest in performing transradial (TR) procedures in the United States, but with so few experienced operators, developing a TR program often means figuring out a lot on one's own. Certain necessary fundamentals - including a good reason for doing procedures transradially, getting adequate training, gaining the support of cath lab staff, using the right equipment, and having patience and perseverance through learning and change - improve the chances of success. In discussing each of these fundamentals, this article reviews the advantages of a radial approach compared with a femoral approach; describes ways to acquire TR training; stresses the importance of involving nurses, technicians, administrators, and colleagues in the process; encourages the use of designated radial equipment for enhancing success; and demonstrates the learning curve by describing a single operator experience during the first year of launching a TR program.

Abstract

The objective of this study is to evaluate the predictive value of the index of microcirculatory resistance (IMR) in patients undergoing primary percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI).Despite adequate epicardial artery reperfusion, a number of patients with STEMI have a poor prognosis because of microvascular damage. Assessing the status of the microvasculature in this setting remains challenging.In 29 patients after primary PCI for STEMI, IMR was measured with a pressure sensor/thermistor-tipped guidewire. The Thrombolysis In Myocardial Infarction (TIMI) myocardial perfusion grade, TIMI frame count, coronary flow reserve, and ST-segment resolution were also recorded.The IMR correlated significantly with the peak creatinine kinase (CK) (R = 0.61, p = 0.0005) while the other measures of microvascular dysfunction did not. In patients with an IMR greater than the median value of 32 U, the peak CK was significantly higher compared with those having values 32 U compared with

Abstract

Although cardiovascular mortality for men has been declining, the number of women dying from cardiovascular disease has slightly increased. Differences between women and men have been identified throughout the entire spectrum of ischemic heart disease, from risk factors to presentation and from diagnosis to treatment and outcomes. In the setting of an acute coronary syndrome or acute myocardial infarction, women are significantly more likely than men to report multiple non-chest pain symptoms, including dyspnea, nausea/vomiting, abdominal pain, back pain, neck pain, and jaw pain. Investigations into the pathophysiology of ischemic heart disease in women have broken away from the traditional thinking that coronary artery disease simply equals epicardial stenosis. In women, the new paradigm of coronary artery disease also focuses on diffuse atherosclerosis, endothelial dysfunction, and microvascular disease. Further research focusing on sex differences in cardiovascular disease is needed, but enough is currently known to offer a sex-based approach, which may ultimately lead to improved outcomes.

Abstract

Contrast-induced nephropathy (CIN) remains an important complication of angiographic procedures, particularly among patients with significant renal impairment. To date, vasodilator therapies such as fenoldopam have failed to prevent CIN, possibly because significant hypotension as a result of systemic infusion has limited the ability to deliver adequate drug levels to the renal vasculature. We present a case of averted CIN after multivessel coronary intervention in a diabetic patient with severe renal insufficiency, potentially due to bilateral renal arterial infusion of fenoldopam. Our subsequent experience with intrarenal fenoldopam in nine additional procedures in eight other high risk patients resulted in one case of asymptomatic transient CIN. Further studies are warranted to evaluate the efficacy of intrarenal administration of vasodilator therapies such as fenoldopam for the prevention of CIN.

Abstract

We sought to determine the incidence, clinical features, and risk factors for retroperitoneal hematoma (RPH) after percutaneous coronary intervention (PCI).Little is known about the clinical features, outcomes, and determinants of this serious complication in the contemporary era of PCI.A retrospective analysis yielded 26 cases of RPH out of 3,508 consecutive patients undergoing PCI between January 2000 and January 2004. Cases were compared with a randomly selected sample of 50 control subjects without RPH.The incidence of RPH was 0.74%. Features of RPH included abdominal pain (42%), groin pain (46%), back pain (23%), diaphoresis (58%), bradycardia (31%), and hypotension (92%). The mean systolic blood pressure nadir was 75 mm Hg. The hematocrit dropped by 11.5 +/- 5.1 points from baseline in RPH patients, as compared with 2.3 +/- 3.3 points in controls (p < 0.0001). The mean hospital stay was longer in RPH patients (2.9 +/- 3.8 days vs. 1.7 +/- 1.5 days, p = 0.06). The following variables were found to be independent predictors of RPH: female gender (odds ratio [OR] 5.4, p = 0.005), low body surface area (BSA <1.73 m(2); OR 7.1, p = 0.008), and higher femoral artery puncture (OR 5.3, p = 0.013). There was no association between RPH and arterial sheath size, use of glycoprotein IIb/IIIa inhibitors, or deployment of a vascular closure device.Female gender, low BSA, and higher femoral artery puncture are significant risk factors for RPH. Awareness of the determinants and clinical features of RPH may aid in prevention, early recognition, and prompt treatment.

Abstract

An emotionally-distressed, elderly Caucasian woman presented with chest pain and hypertension. Electrocardiogram showed inferior ST-segment elevation, and an urgent cardiac catheterization was performed. Coronary angiography revealed normal appearing coronary arteries; however, left ventriculography showed extensive left ventricular apical akinesis. The patient had a mild rise in cardiac enzyme levels indicative of myocardial injury. She was discharged after an uncomplicated in-hospital course. One month later, the left ventricular wall motion abnormality had improved. In this report, the authors discuss this compilation of findings known as tako-tsubo-like left ventricular dysfunction.

Abstract

Pharmaceutical companies spent US$1.8 billion on direct-to-consumer advertisements for prescription drugs in 1999. Our aim was to establish what messages are being communicated to the public by these advertisements.We investigated the content of advertisements, which appeared in ten magazines in the USA. We examined seven issues of each of these published between July, 1998, and July, 1999.67 advertisements appeared a total of 211 times during our study. Of these, 133 (63%) were for drugs to ameliorate symptoms, 54 (26%) to treat disease, and 23 (11%) to prevent illness. In the 67 unique advertisements, promotional techniques used included emotional appeals (45, 67%) and encouragement of consumers to consider medical causes for their experiences (26, 39%). More advertisements described the benefit of medication with vague, qualitative terms (58, 87%), than with data (9, 13%). However, half the advertisements used data to describe side-effects, typically with lists of side-effects that generally occurred infrequently. None mentioned cost.Provision of complete information about the benefit of prescription drugs in advertisements would serve the interests of physicians and the public.